An on-wafer fabricated free-chlorine sensor

Abstract

A method for on-wafer fabrication of free-chlorine sensors is described. The sensor structure consists of a planar three-electrode electrochemical cell covered with a polyHEMA hydrogel membrane. This membrane is photolithographically patterned on-wafer. In order to guarantee a good adhesion of the membrane to the electrode surface a special oxidation consisting of a treatment in an oxygen plasma has been developed followed by a silanization procedure. The optimal operational polarization voltage for detection of free chlorine was found to be +50 mV vs. SCE. Sensors with membrane thicknesses of 10 and 50 mu m were found to give approximately linear calibration curves between 0.1 and 5 mg/1 free chlorine, with sensitivities of 2 and 0.4 nA/(mg/1), respectively.<>